Reporting communication link information

ABSTRACT

A method for reporting link information in a communication system including a communication terminal and a plurality of transceivers with each of which the communication terminal can communicate over a respective communication link; the method comprising: the communication terminal determining link information for each of the communication links; and the communication terminal periodically transmitting link messages, each link message containing link information for a first set of the communication links, and the link messages being formatted such that groups of successive link messages collectively contain link information for a larger set of the communication links.

This invention relates to a method for reporting information oncommunication links, for example link quality information, in atelecommunications system such as a cellular radio telecommunicationsnetwork.

FIG. 1 shows schematically the configuration of a typical cellular radiotelecommunications network. The network comprises a number ofbase-stations (BSs) 1, 2, 3 etc. Each base-station has a radiotransceiver capable of transmitting radio signals to and receiving radiosignals from the area of a cell 4, 5, 6 etc. next to the base-station.By means of these signals the base-station can communicate with a mobilestation (MS) terminal 7 in that cell, which itself includes a radiotransceiver. Each base station is connected to a mobile systemcontroller (MSC) 8, which is linked in turn to the public telephonenetwork 9 and/or to other networks such as packet data networks. Bymeans of this system a user of the MS 7 can establish a telephone callto the public network 9 via a BS in whose cell the MS is located.

The location of the MS could be fixed (for example if it is providingradio communications for a fixed building) or the MS could be moveable(for example if it is a hand portable transceiver or “mobile phone”).When the MS is moveable it may move between cells of the cellular radiosystem. As it moves from one cell (the “old cell”) to another cell (the“new cell”) there is a need to hand it over from communication with theBS of the old cell to the BS of the new cell without dropping the calldue to a break in communications between the mobile station and thenetwork. This process is known as handover. A need can also arise tohand over a MS whose location is fixed, for example if atmosphericconditions affect its communications with the old BS and call qualitycan be improved by handing it over to another BS or if there is a needto free up capacity of the old BS.

In some systems, for example the wideband code division multiple access(W-CDMA) system proposed for the Universal Mobile Telephony System(UMTS), a mobile station is capable of making traffic communicationswith more than one base station at one time. This macrodiversityarrangement allows greater reliability of communications and can reducethe required transmission power. It also means that handovers betweenone base station and another can be performed in a gradual (“soft”)rather than an abrupt (“hard”) way.

It is conventional for the system to include apparatus for controllinghandover and macrodiversity. That apparatus could be on the network side(for example at the MSC) or the mobile side of the air interface betweenthe MS and a BS, or could be distributed between the two. That apparatusconventionally receives information relating to the quality of potentialcommunications between the MS and at least some of the BSs andoptionally other information such as data on the load on at least someof the BSs. Using this information the apparatus determines which basestation(s) an MS should communicate with and issues instructions to theBSs and the MS accordingly.

For the W-CDMA system it is proposed, in line with existing systems suchas GSM, that a mobile station will transmit to the network measurementreports on communication quality with six nearby cells. For example,according to the GSM standard a report on a nearby (“neighbouring”) cellwill occupy 17 reserved bits in a standard reporting message of 107bits. The reporting message can therefore contain reports on only sixnearby cells. Such reporting message is to be sent by a mobile stationin each multiframe—i.e. once every 480 ms.

The inventors of the present invention have identified that especiallyin multisystem or multiband networks and/or in cellular communicationsystems operating in a multilayer environment the number of cells withwhich the mobile station may interact might often be greater than six.It could therefore be advantageous for a mobile station to be able totransmit measurement reports for more than six cells. This would beespecially advantageous in multisystem or multiband networks and/or incellular communication systems operating in a multilayer environment. Ingeneral, multimode systems can be defined as communication environmentswhere the mobile station may be in a service area where it can be servedby more than one serving network, system, standard, frequency or thelike. An example of a multiband system is a system in which a dual-bandmobile station can be served by GSM (Global System for MobileCommunications) networks operating at 900 MHz and 1800 MHz. Anotherexample is a system in which a mobile station can be served by a GSMnetwork and a UMTS/W-CDMA network, or a GSM network and a DAMPS network.

It would thus be desirable for a mobile station to be able to report onpotential communications links with more than six cells. One way inwhich this could be achieved is by lengthening the reporting message togive room for measurement reports on more than six cells. However, thiswould have major problems of incompatibility with existing systems.Another possibility would be for the level of reporting to be altered soas to occupy fewer than 17 bits. However, as well as problems ofincompatibility with existing systems, this solution would be expectedto reduce the reporting accuracy and therefore the precision of handoverdecisions.

WO 98/57512 discloses an arrangement where a measurement report istransferred to a network during the first available slow associatedcontrol channel periods. The measurement report contains data that themobile terminal obtained while it was waiting in the idle mode. Duringsubsequent slow associated control channel periods, the mobile terminaltransfers measurement information to the network based on the dataobtained in the active mode.

There is therefore a need for a practical method whereby a mobilestation can transmit reporting messages on links with an increasednumber of cells. Such a method should preferably be capable of retaininga degree of consistency with existing standards and standardisationproposals. By this means, the method may preferably enhance multisystem,multiband and/or multimode operation. It is one aim of the presentinvention to at least partially address one or more of the above issues.

According to one aspect of the present invention there is provided amethod for reporting link information in a communication systemincluding a communication comprising, the communication terminaldetermining link information for each of the communication links, andthe communication terminal periodically transmitting link messages, eachlink message containing link information for a first set ofcommunication links, and the link messages being formatted in accordancewith a predetermined scheme such that groups of successive link messagescollectively contain link information for a set of communication linkslarger than the first set of communication links.

The said larger set is suitably larger than the first set of thecommunication links. The method preferably includes the step of definingthe said larger set, for example by selecting communication links toform the said larger set.

Preferably link information for at least one of the communication linksis contained in each of successive link messages. For instance, eachsuccessive link message may contain link information for one, two ormore of the communication links, whilst link information for others ofthe communication links is not contained in every link message. Thatlatter link information may be sent in link messages spaced apart by aset amount, for example every two or three link messages, or asdetermined by a less strict periodic or aperiodic scheme.

It is thus preferred that successive link messages contain linkinformation for at least one communication link in common. It is alsopreferred that link messages spaced apart by a set interval—for exampleby one, two or three other messages—regularly contain link informationfor the same ones of the communication links.

The method may comprise the step of determining a subset of thecommunication links having the best link according to a selectedmeasure, and wherein link information for the communication links ofthat subset is contained in each of successive link messages. The subsetpreferably consists of one communication link, or alternatively of twocommunication links.

It is preferred that periodically link messages contain link informationfor the same ones of the communication links.

The communication terminal is preferably capable of transmitting thelink information in a plurality of schemes according to which linkinformation is distributed between successive link messages. Suchschemes may involve transmitting link information for a set of thecommunication links in alternate link messages, or in every third linkmessage.

The communication system suitably includes a control unit (e.g. an MSCor the like) coupled to the transceivers. The method suitably comprisesthe step of causing at least one of the transceivers to transmit ascheme selection signal to the communication terminal indicative of theone of the plurality of schemes to be used by the communicationterminal. The scheme selection signal may be transmitted on a broadcastchannel. The scheme selection signal may be transmitted as part of asystem information message. The method may suitably comprise the step ofoperating the communication terminal in response to the scheme selectionsignal so as to use the scheme indicated by the scheme selection signal.

The link messages may be transmitted over at least one of the saidcommunication links. The link messages may be each sent in a respectivemultiframe. (The multiframe may be defined by reference to normalcommunications over the said communication links).

Each link message preferably contains link information for six of thecommunication links, and most preferably for only six of thecommunication links.

The link information for a communication link is preferably in some wayindicative of the quality of communications over that link. The linkinformation may, for example be indicative of received signal strengthinformation for communications over the link—for example of the strengthof received broadcast signals over the link.

The method may suitably comprise the steps of receiving the linkinformation and making a handover decision for the communicationterminal on the basis of the link information. That decision may be madeat an MSC or like equipment.

The method may comprise the step of the communication terminalsignalling that it is capable of operating so as to transmit successivelink messages containing link information for different ones of thecommunication links. That signalling may be performed on establishmentby the communication terminal of a connection with the system.

According to the present invention from a second aspect there isprovided a communication system comprising a communication terminal, aplurality of transceivers with each of which the communication terminalcan communicate over a respective communication link; a communicationterminal comprising link measurement means for measuring linkinformation for each of the communication links, transmission means forperiodically transmitting link messages, each link message containinglink information for a first set of communication links, link messageforming means for forming the link messages in accordance with apredetermined scheme such that groups of successive link messagescollectively contain link information for a set of communication linkslarger than the first set of communication links.

According to the present invention, third aspect there is provided acommunication terminal for operation in a radio telecommunicationssystem the terminal comprising communication means for communicatingwith one or more of a plurality of radio transceivers, measurement meansfor measuring a quality of signals received from each of the saidtransceivers over respective communication link, and measurement messagegeneration means for generating measurement messages for transmission bythe communication means, each measurement message containing measuredquality information for a first set of the communication links, themeasurement message generation means being capable of generating aseries of measurement messages in accordance with a predeterminedscheme, wherein groups of successive measurement messages collectivelycontain measured quality information for a set of communication linkslarger than the first set of communication links.

Optional additional features of the second and third aspects of thepresent invention include features analogous to those set out above inrelation to the first aspect of the present invention.

The communication terminal may be a radio and/or cellular telephone.Each transceiver may be a base station transceiver of a radio telephonesystem. The communication system may suitably be a cellular telephonenetwork. The communication terminal may suitably be capable ofcommunicating by radio with one or more, and preferably all, of thetransceivers.

The present invention will now be described by way of example withreference to the accompanying drawings, in which:

FIG. 1 shows schematically the configuration of a typical cellular radiotelecommunications network;

FIG. 2 shows a schematic diagram of some components of a mobile station;and

FIG. 3 illustrates signal flow in a measurement reporting arrangement.

The present reporting method and associated apparatus will be describedbelow with general reference to the GSM system and to the proposedUMTS/W-CDMA standard, but it will be understood that the method isanalogously applicable to provide enhanced reporting in othertelecommunications systems.

The present reporting method involves increasing the number of cells onwhich measurement reports may be sent by reducing the frequency withwhich reports are sent on nearby (“neighbouring”) cells. Thus,successive measurement report messages may include measurement data fordifferent sets of nearby cells. In other words, measurement reports onneighbouring cells may be transmitted with different frequencies. Suchfrequencies may be the same or different. In a preferred arrangement,the mobile station determines a set of neighbours providing the bestlinks to it; measurement reports are then sent for those cells in everyreport message, whereas information on other links is sent lessfrequently—for example in every second or third report message.

To avoid ambiguity, it should be noted that the term “neighbouring” isgenerally used to refer to any further cell that can be reached by amobile station in a cell of the cellular communication system, withoutsuch a cell having to actually border any cell with which the mobilestation is currently communicating. Thus “neighbouring” cells willtypically be wholly or partly overlapping. Neighbouring cells may becells of another communication network or cells of another frequency.This is the case when, for example, dual-band mobile stations are used.

FIG. 1 which shows a cellular network. It should be appreciated thatalthough FIG. 1 shows base stations which each provide anomnidirectional cell, embodiments of the present invention may beimplemented using any appropriate configuration of cells. It is alsonoted that the radio coverage area defining a cell may consist of asector of a base station provided with a directional or sector antenna(not shown in FIG. 1). Such a sector base station may use e.g. three120° directional antennas whereby three radio coverage areas areprovided, or four 90° directional antennas providing four radio coverageareas and so on, or any combinations of different radio coverage beamwidths. It should also be appreciated that base stations may sometimesbe referred to as node B (e.g. in the UMTS standard). For simplicity itwill be assumed herein that each cell is associated with a single basestation transceiver unit (BTS).

In FIG. 1 each radio coverage area or cell is served by the respectivebase transceiver station BTS 1, 2, 3 etc. Each base transceiver stationBTS is arranged to transmit signals to and receive signals from themobile station MS 7 in the cell. Likewise, the mobile station is able totransmit signals to and receive signals from a respective basetransceiver station. The mobile station 7 accomplishes this via wireless(preferably radio) communication with the base stations. Typically anumber of mobile stations will be in communication with each basestation although only one mobile station is shown in FIG. 1 for clarity.

Each of the base stations is connected to a network controller, which inone form of the exemplifying GSM system comprises a base stationcontroller (BSC) 10 connected further to a Mobile Switching Centre (MSC)9. In the described embodiment the MSC is used as a network controller.In some arrangements the base station controller 10 controlling one orseveral base stations between the network controller and the basestations may be omitted. The network controller controls its servicearea, i.e. the cells and base stations connected to it, either directlyor via the base station controller. It is noted that typically more thanone network controller is provided in a network. The network controlleris connected to other elements or parts of the telecommunicationsnetwork system via a suitable linking or gateway apparatus, such asGateway Mobile Switching Centre (GMSC; not shown).

The implementation of the basic communication formatting between themobile station, the base station and the controller in GSM andUMTS/W-CDMA systems is known, and will thus not be discussed in moredetail herein. It is sufficient to note that the interface may comprisechannels in both uplink and downlink directions between the mobilestation in the cell associated with a given base station and that theinformation sent to the mobile station and the data may be sent in anysuitable format. The messages sent from the mobile stations may includeinformation identifying the mobile station (for instance, MS ID and/orIMSI (Mobile Station Identity and/or International Mobile SubscriberIdentity, respectively)).

As also illustrated in FIG. 1, the mobile station can be simultaneouslyin the signalling or coverage area of several cells and their associatedbase stations. The mobile station is arranged to perform measurements inorder to be able to provide information based on which a suitable cellcan be selected for serving the mobile station. In other words, inaddition to controlling the ongoing connection with the servicing basestation, the mobile station performs measurements concerning theneighbouring cells as well. These measurements may be of any appropriatefeature that is in some way indicative of the quality of potentialtraffic communications over the link between the mobile station and thatcell; examples are signal strength of the base station for the cell asreceived at the mobile station, error rate of communications from thatbase station (e.g. bit error rate or frame error rate), or delay ordistortion of such communications.

FIG. 2 shows in more detail a mobile station capable of operation in thesystem of FIG. 1. The mobile station, which in this case is a cellulartelephone, includes a radio transceiver unit 20. a measurement unit 21and a control unit 22. These may be implemented as distinct units asillustrated in FIG. 2 or by software running on common hardware.

The transceiver 20 transmits traffic signals to and receives trafficsignals from one or more base stations to which the mobile station iscurrently attached. The transmissions to and from the mobile station aresplit into multiframes, each of which occupies 480 ms. The transceiveralso receives signals from other base stations, typically signals on oneor more broadcast channels e.g. BCCH. These signals as well as signalsreceived from the base station(s) to which the mobile station isattached are directed to the measurement unit 21. The measurement unitmeasures a feature of those signals as mentioned above—for examplereceived signal strength. The measurement results are passed to thecontrol unit 22 which generates measurement reports according to ascheme that will be described below. The measurement reports are thentransmitted to the base station(s) to which the mobile station isattached. The measurement reports are then used by the network to makehandover decisions.

The measurement reports themselves are suitably of a known format, forexample of 107 bits including 17 bits per cell/base station that isbeing reported on.

The scheme used by the control unit may be one of a number of schemes,example schemes being described below.

Reporting Scheme 0

For reasons of backwards compatibility the control unit is capable oftransmitting measurement reports in which each successive measurementreport includes measurement information for communication links with thesix cells determined by the control unit to be the best (e.g. beingreceived most strongly or with fewest errors). Thus it will normally bethe case that successive messages will include data relating to the samesix cells.

Reporting Scheme 1

The measurement unit measures data for links with up to 10 neighbouringcells. These cells will be termed N1 to N10. The two best cells areselected by the control unit. These are, for example, the two that arereceived with the highest signal level. Measurement data for these cells(N1 and N2, say) is sent in every multiframe (MF)—that is every 480 ms.Measurement data for each of the remaining 8 neighbours (N3–N10) isdistributed between successive multiframes so as to be sent every secondmultiframe—that is every 960 ms

The structure of successive measurement reports under this system, witheach measurement report including slots for data on measurements of sixcell links, is shown in the following table:

Measurement Report Multiframe Multiframe Multiframe Slot Number n n + 1n + 2 . . . 1 N1 N1 N1 . . . 2 N2 N2 N2 . . . 3 N3 N4 N3 . . . 4 N5 N6N5 . . . 5 N7 N8 N7 . . . 6 N9  N10 N9 . . .

The values reported for the neighbours N3–N10 could be an averaged valueof measurements over the appropriate two multiframe period before whichthey are sent, so little or no information is lost. Alternatively thefirst, second, higher or lower value measured for each of neighboursN3–N10 over the period could be sent.

Reporting Scheme 2

The measurement unit measures data for links with up to 15 neighbouringcells. These cells will be termed N1 to N15. The best neighbour (N1) isidentified and a report transmitted for it every 480 ms. The 2nd to 7thbest neighbours (N2–N7) are identified and a report transmitted for eachof them every 960 ms. The remaining 8 neighbours (N8–N15) are reportedon every 1920 ms.

The structure of successive measurement reports under this system, witheach measurement report including slots for data on measurements of sixcell links, is shown in the following table:

Measure- ment Report Slot Number MF n MF n + 1 MF n + 2 MF n + 3 MF n +4 . . . 1 N1 N1 N1 N1 N1 . . . 2 N2 N3 N2 N3 N2 . . . 3 N4 N5 N4 N5 N4 .. . 4 N6 N7 N6 N7 N6 . . . 5 N8 N9 N10 N11 N8 . . . 6 N12 N13 N14 N15N12 . . .

Note that the value reported for the neighbours N2–N7 could be anaveraged value over the two multiframes between reports on them, and thevalue reported for N8–N15 could be an average over the four multiframeperiods between reports on them, so little or no information may belost. Alternatively, one of the other selection procedures describedabove could be used.

Reporting Scheme 3

In this scheme the control unit 22 of the mobile station ranks (e.g. onthe basis of received signal level) the quality of the links withneighbouring base stations. The reporting rate for each neighbour isdetermined by its ranking.

In a first approach the mobile can re-evaluate the ranking of theneighbours and therefore their reporting rate each 2^(nd) multiframe(960 ms). In order to do so the averaged value of the signal level overthe previous 2 multiframes can be used.

There would be two options to perform such averaging:

-   1. The mobile stores all the individual values determined over the 2    multiframes. In the worst case this would require it to store 2    received signal level (RxLev) values (of conventionally 6 bits    each), for example for a maximum of, say, 15 neighbours. This would    requires a total of 180 bits of memory 23 in the control unit 22 of    the mobile.-   2. Ongoing averaging. The averaging can be an ongoing averaging in    order to minimise the required memory. If this approach is used    selected the memory required in the mobile would be only 90 bits.    Example:

Multiframe 1 2 RxLev 30 45 Average 30 37.5

Alternatively, the mobile could re-evaluate the ranking of theneighbours and therefore their reporting rate each 4^(th) multiframe(1920 ms). In order to do so the averaged value of the signal level overthe previous 4 multiframes could be used.

In order to do so there would be two options:

-   1. The mobile stores all the values measured over the 4 multiframes.    In the worst case this would require to store 4 RxLev values (6 bits    each) for a maximum of, say, 15 neighbours. This requires a total of    45 bytes of memory in the mobile.-   2. Ongoing averaging. The averaging can be an ongoing averaging in    order to minimise the required memory. If this approach was selected    the memory required in the mobiles would be only 90 bits. Example:

Multiframe 1 2 3 4 RxLev 30 45 33 60 Average 30 37.5 36 42

This scheme provides an extremely flexible way for the mobile station tosend measurement information from more cells to the network.

The schemes 1 to 3 described above provide the facility to transmitmeasurement reports on links with neighbouring cells at different ratesdepending on their signal level ranking.

The mobile station may automatically select an appropriate reportingscheme, or the network may indicate to the mobile station whichreporting scheme is to be used. In the latter case, the indication maybe by means of a scheme indication signal, which could be sent over abroadcast channel, for example the BCCH, and for example as part of theBCCH System Information message. This would allow network operators tocontrol the introduction and operation of the enhanced reporting schemesdescribed above. The use of two bits forming the scheme indicationsignal would allow the implementation of 4 different reporting modes.FIG. 3 illustrates the signal flow in such an implementation.

Preferably, mobiles that are able to offer the enhanced reportingschemes 1 to 3 described above should signal the availability of suchschemes to the network. This may, for example be done each time theyestablish a connection to the network. At that time the mobilessupporting the above functionality may preferably inform the networkthat they are “alternative neighbour reporting compliant”, so thenetwork knows the available formats of neighbour reporting for aconnection with those mobiles.

The selection of the relevant cells for reporting may be based on anyappropriate predefined rule of selection. The rules may be defined inthe standards the mobile station and/or the communication system arearranged to use. The rules may be stored permanently in the mobilestation. According to one possibility the rules are stored in anappropriate network element and transmitted therefrom to the mobilestation when ever required. The rules for selecting relevant cells mayalso be changed when this is deemed necessary. The selection of therelevant cells may be based, with no limitation to the following, on themeasured signalling levels, used radio frequencies, direction of themovement of the mobile station, loading conditions of the neighbouringcells and so on.

In some of the schemes described above it is possible that resolution ofneighbour cell measurement information could be lost due to theincreased period between transmissions of some neighbour data. This canbe mitigated or even overcome by means of pre-averaging averaging ofindividual measured values by the control unit 22 of the mobile station.If the mobile performs pre-averaging of the raw information that iscollected by the measurement unit 21, then no information would be lostas the reported values for those neighbours with slower reporting ratewill contain the averaged value of all the available information. Manynetworks are, in any event, configured to average the neighbour valuesreported by mobiles. In the system described above, since the networkshould know the reporting method used by each connection with a mobileand should know the reporting rate of each reported neighbour, it couldapply a different averaging to each neighbour. Therefore, from a systemperspective the performance of the standard and the alternate reportingmethods could be enhanced, as the result after the averaging is thesame, but the number of neighbours available to the system could bedramatically increased.

The period between measurement report messages is, of course,system-dependant and could be greater or less than 480 ms.

In view of the foregoing description it will be evident to a personskilled in the art that various modifications may be made within thescope of the invention as defined by the accompanying claims.

1. A method for reporting link information in a communication systemincluding a communication terminal and a plurality of transceivers witheach of which the communication terminal can communicate over arespective communication link; the method comprising: the communicationterminal determining link information for each of the communicationlinks; and the communication terminal periodically transmitting linkmessage, each link message containing link information for a first setof the communication links, and the link messages being formatted suchthat groups of successive link messages collectively contain linkinformation for a larger set of the communication links.
 2. A method asclaimed in claim 1, wherein link information for at least one of thecommunication links is contained in each of successive link messages. 3.A method as claimed in claimed 2, comprising the step of determining asubset of the communication links having the best link according to aselected measure, and wherein link information for the communicationlinks of that subset is contained in each of successive link messages.4. A method as claimed in claim 3, wherein the subset consists of twocommunication links.
 5. A method as claimed in claim 4, whereinperiodically link messages contain link information for the same ones ofthe communication links.
 6. A method as claimed in claim 2, wherein thecommunication terminal is capable of transmitting the link informationin a plurality of schemes according to which link information isdistributed between successive link messages.
 7. A method as claimed inclaim 6, wherein the communication system includes a control unitcoupled to the transceivers, and the method comprises the step ofcausing at least one of the transceivers to transmit a scheme selectionsignal to the communication terminal indicative of the one of theplurality of schemes to be used by the communication terminal.
 8. Amethod as claimed in claim 7, wherein the scheme selection signal istransmitted on a broadcast channel.
 9. A method as claimed in claim 7,wherein the scheme selection signal is transmitted as part of a systeminformation message.
 10. A method as claimed in claim 7, comprising thestep of operating the communication terminal in response to the schemeselection signal so as to use the scheme indicated by the schemeselection signal.
 11. A method as claimed in claim 7, wherein one of theschemes involves transmitting link information for a set of thecommunication links in alternate link messages.
 12. A method as claimedin claim 7, wherein one of the schemes involves transmitting linkinformation for a set of the communication links in every third linkmessage.
 13. A method as claimed in claim 12, wherein the link messagesare transmitted over at least one of the said communication links.
 14. Amethod as claimed in claim 13, wherein each link message is sent in arespective multiframe of communications over the said communicationlinks.
 15. A method as claimed in claim 14, wherein each link messagecontains link information of six of the communication links.
 16. Amethod as claimed in claim 15, wherein the link information for acommunication link is indicative of the quality of communications overthat link.
 17. A method as claimed in claim 16, comprising the steps ofreceiving the link information and making a handover decision for thecommunication terminal on the basis of the link information.
 18. Amethod as claimed in claim 17, comprising the step of the communicationterminal signaling that it is capable of operating so as to transmitsuccessive link messages containing link information for different onesof the communication links.
 19. A method as claimed in claim 18, whereinthe step of the communication terminal signaling that is capable ofoperating so as to transmit successive link messages containing linkinformation for different ones of the communication links is performedon establishments by the communication terminal of a connection with thesystem.
 20. A method as claimed in claim 19, wherein the communicationterminal is a radio telephone.
 21. A method as claimed in claim 20,wherein each transceiver is a base station transceiver of a radiotelephone system.
 22. A communication system comprising: a communicationterminal; a plurality of transceivers with each of which thecommunication terminal can communicate over a respective communicationlink; the communication terminal comprising link measurement means formeasuring link information for each of the communication links;transmission means for periodically transmitting link messages, eachlink message containing link information for a first set of thecommunication links; and link message forming means for forming the linkmessages such that groups of successive link messages collectivelycontain link information for a larger set of the communication links.23. A communication terminal for operation in a radio telecommunicationssystem, the terminal comprising: communication means for communicatingwith one or more of a plurality of radio transceivers; measurement meansfor measuring a quality of signals received from each of the saidtransceivers over a respective communication link; and measurementmessage generation means for generating measurement messages fortransmission by the communication means, each measurement messagecontaining measured quality information for a first set of thecommunication links; the measurement message generation means beingcapable of generating a series of measurements messages wherein groupsof successive measurement messages collectively contain measured qualityinformation for a larger set of the communication links.
 24. A controlunit for operating in a communication system, the communication systemincluding a communication terminal and a plurality of transceivers witheach of which the communication terminal can communicate over arespective communication link, the communication system being arrangedto perform a method of reporting link information comprising: thecommunication terminal determining link information for each of thecommunication links; and the communication terminal periodicallytransmitting link messages, each link message containing linkinformation for a first set of the communication links, and the linkmessages being formatted in accordance with a predetermined scheme suchthat groups of successive link messages collectively contain linkinformation for a set of communication links larger than the first setof communication links; the control unit being coupled to thetransceivers and being arranged to cause at least one of thetransceivers to transmit a scheme selection signal to the communicationterminal indicative of the one of the plurality of schemes to be used bythe communication terminal.